Mercury vapor switch



Dec. 27, 1949 w, G, TAYLOR 2,492,669

' MERCURY VAPOR SWITCH Filed July 1, 1944 IN VEN TOR.

BY CQGAL, om.

Patented Dec. 27,A 1949 UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to a mercury arc switch. It was designed for a particular application, namely to break the primary circuit in welding apparatus. It should be of use wherever it is desired to break a direct circuit cleanly.

In concurrently filed application, Serial No. 543,190, filed July l, 1944, the applicant described the reasons for such a switch and disclosed a vacuum tube switch wherein two graphite electrodes are separated inside a vacuum so as to break the primary circuit of welding apparatus. The present invention has the same general objective, but accomplishes its end by forming a mercury vapor arc as part of the conductive primary circuit of the welding apparatus and then snufng out this arc so as to collapse the circuit suddenly. The particular embodiment by which applicant accomplishes this end is shown in a single figure in the drawings wherein Figure 1 shows a schematic welding circuit with a cross section of applicants mercury arc switch tube.

Continuing to refer to the drawings, the numeral I identifies a direct current source of power having its negative post connected by a conductor to a switch I4. The conductor I6 connects the switch I4 to the primary winding I8 of a transformer 20. The primary circuit is completed by a conductor 22 connected to a post 24 on an evacuated tube 26. This tube constitutes applicants mercury arc switch. A post 28 on the tube 26 is connected by a conductor 30 to a low resistance solenoid 32. The solenoid 32 is connected to the direct current source of power by a conductor 34.

Referring to the transformer 28, its secondary winding 36 is connected by conductors 38 and 40 to electrodes 42 and 44 respectively of welding apparatus-all of which, is schematically shown.

Returning now to the mercury arc switch 2li, this is composed o f a glass envelope 4E which has an inwardly `directed hollow post 48 and a projection forming a recess 58 directed outwardly along the long axis of the tube. Extending along the longer dimension of this tube 26 is a tungsten rod 52 whose purpose it is to act as a starter. This tungsten rod 52 is held in vertical reciprocal position by means of a hollow hard graphite casing 54 which is supported by means of a shoulder 56 mounted on a ceramic tube 58, which ,in turn is seated permanently in the glass hollow post 48, The lead 28 is made of tungsten and extends inwardly through the ceramic tube 58 and supports at its inner end a tungsten anode 60 which is shapedv The graphite casinig like a ring or annulus. 54 has an opening 62 which snugly fits the tungsten rod 52 and acts as a vertical guide for up and down movement. On the side of the casing 54 opposite to the opening 62 is a larger opening 64. The rod 52 passes through the center of this and at its lower end there is placed a disc made of graphite 66. Depending to a point below the disc 68 is the lower end or conductive contact 68 having a point 13 of the graphite rod 52. The bottom 18 of the tube is filled with mercury 12, which acts as an emitting cathode when coupled to the negative side 0f a direct current circuit.

Positioned on the upper end of the rod 52 is an iron armature 14, of a size and shape which is adapted to move readily in and out of the glass projection 50. Tapped to the rod 52 is a flexible conductor 16 connected to a lead-in post 18. This post is connected by a conductor to a second solenoid 82 positioned around the glass projection 50, and closer to the iron armature 14 than is the solenoid 32. The solenoid 82 has highr resistance and is connected by a conductor 84 to the line 34.

The glass envelope 46 is evacuated.

This mercury are switch functions as follows. When the welding apparatus operator closes the switch I4, the primary circuit is completed to.

the transformer 26 by the conductors I6, I8, 22, 24, mercury 12, 68, 52, 16, 18, 86, 82, 84 and 34. The high resistance solenoid 82 pulls the iron armature 14 upwardly into position 2 and in so doing the tip 13 of the lower end .of the tungsten rod 68 starts an arc from the mercury pool as it leaves the pool. This arc closes the primary circuit of the transformer 20 from the mercury pool 12 to the kanode 60. The primary circuit through the transformer 26 is now being completed by the mercury vapor arc which closes the circuit through the anode 60, lead 28, conductor 3l! and low resistance solenoid ,32. By this. time the current is built up in the transformer 28 and the armature 14 now moves into position 3. In so doing, the disc 66 moves into position 3 and snuifs out the mercury vapor arc. As is Vwell understood in the art, the mean free path required for a mercury vapor arc is about 4/1000 of an inch, or at least' a small part of an inch. In order to snuff out the mercury .vapor arc, therefore, the disc 6,6. need not seat itself over the opening B4 with the greatest precision. Approximate tightness is sufficient. This also accounts for the" fact that the mercury vapor arc will not go around the casing 54 to go in around the rod 52 in between the rod 52 and the hole B2.

The snuffing out of the vapor arc collapses the eld in the primary windings of the transformer 20 very suddenly and causes the surge of current in the secondary which is so desirable in welding.

As long as the switch I4 is in closed position, the tungsten rod 52 will remain in position 3. As soon as the switch I4 is open, the tungsten rod 52 will drop by gravity into position l. It will be appreciated that a spring or some other device may be used to urge the tungsten rod 52 vertically.

In this switch, the poles of the source of vpower may not be reversibly connected to the posts of the tube. The lead 28 is an anode and must be connected to the positive side of the source of power.

In place of the mercury pool, a hot cathode, as for example an oxide coated cathode may be substituted. In such a structure', the direct contact from the hot cathode will be broken by the activity of a high resistance solenoid in much the same way shown in a mercury vapor switch. When the direct contact has been broken, the hot cathode will emit to an anode to maintain the primary circuit in operation and bring into action a low resista-nce solenoid which will shut oir the anode and stop the admission by the cathode.

Having thus described my invention, I claim:

l. A self-opening switch for a direct current circuit comprising an evacuated envelope, an-

emitting cathode in the envelope conductively associated with an external post for connection tive side of the circuit, a conductive contact movable into and out of engagement with the cathode, said contact being conductively associated with an external post for connection to the positive side of the circuit, electrical means in this contact circuit for moving the contact out of en" .i

gagement with the cathode, and a closure member associated with this movable Contact for thereafter closing the passageway.

2. A self-opening switch for a direct current circuit comprising an evacuated envelope, a mercury pool in the envelope conductively associated with an external post for connection to the negative side of the circuit, an anode spaced from the mercury pool with a passageway connecting the two, said anode being conductively associated with an external post for connection to the positive side of the circuit, a conductive Contact movable into and out of engagement with the mercury pool, said contact, being conductively associated with an external post for connection to the posi-- tive sideof the circuit, electrical means inV this contact circuit for moving the contact out of engagement withthe mercury-pool, and a closure member associated with this movable contact for thereafter closing the passageway.

3. A self-opening switch for a direct current circuit comprising an evacuated envelope, an emitting cathode in the envelope conductively associated with an external post for connection to the negative side of the circuit, an anode spaced from the cathode with a passageway connecting the two, said anode being conductively associated with an external post for connectionto the' positive side of the circuit, a conductive contact movable into and out of engagement with the cathode, said contact being conductively associated with an external post for connection to the positive side of the circuit, a solenoid in the circuit of the movable contact, an armature actuatable by the solenoid and associated with the movable contact for moving it out of engagement with the cathode, and a closure member associated with this movable contact for thereafter closing the passageway.

4. A self-opening switch for a direct current circuit comprising an evacuated envelope, an emitting cathode in the envelope conductively associated with an external post for connection to the negative side of the circuit, an anode spaced from the cathode with a passageway connecting the two and conductively associated with an external post for connection to the positive side of the circuit, a conductive contact movable into and out of engagement with the cathode, said contact being conductively associated with an external post for connection to the positive side of thecircuit, a closure member movable with the contact for closing the passageway when the contact has moved a selected distance from the cathode, electrical means in the movable contact circuit for moving the contact out of engagement with the cathode, and electrical means in the anode circuit for thereafter moving the closure member across -the passageway.

5. A self-opening switch for a direct current circuit comprising an evacuated envelope having a vertical axis, an axially movable conductive rod disposed along the vertical axis, an armature on the upper end of the rod1 a first solenoid and av second solenoid disposed one above the other and above the armature, an emitting cathode in the bottom of the envelope and contactable by the rod when in its lower position, an anode in the envelope connected by a passageway to the emitting cathode, a closure member mounted on the rod and seatable over said passageway when the rod is in its uppermost position, a conductor connecting the rod to a lead of the rst solenoid, and a conductor connecting the anode to a lead of the second solenoid, whereby when the switch is placed in a direct current circuit with the negative pole connected to the cathode and the positive pole connected to the other leads of the twoV solenoids, the rst solenoid will raise the rod from the cathode starting an arc and a iiow of current 8. A self-opening switch for a direct current circuit comprising an evacuated envelope having a.

vertical axis, a ring anode supported in said envelope with its hole concentric with the envelope axis, a nonconductive casing around said anode having a comparatively large downwardly directed concentric opening therein, a mercury vapor cathode in the bottom of the tube, a rod movably disposed in the vertical axis of the tube so that it passes through the center ring in nonconductive relationship thereto and through the top and bottom opening of the housing and in its lower position contacts the cathode, an armature on the upper end of the rod, a solenoid concentric withl the axis above the armature, a conductor connecting the rod to one lead of the solenoid, anda disc mounted on the bottom of the rod for closing the opening in the casing, whereby when the negative side of a direct current circuit is connected to the cathode of the switch and the positive side is connected to the anode and the lead of the solenoid, the rod will rst start an arc between the cathode and the anode and thereafter the closure member will snuff out the arc.

9. A self -opening switch for a direct current circuit comprising an evacuated envelope having a vertical axis, a ring anode supported in said envelope with its hole concentric with the envelope axis, a nonconductive casing around said anode having a comparatively large downwardly directed concentric opening therein, a mercury vapor cathode in the bottom of the tube, a rod movably disposed in the vertical axis of the tube so that it passes through the center ring in nonconductive relationship thereto and through the top and bottom opening of the housing and in its lower position contacts the cathode, an armature on the upper end of the rod, a solenoid concentric with the axis above the armature, a conductor connecting the rod to one lead of the solenoid, a disc mounted on the bottom of the rod for closing the opening in the casing, and a second solenoid positioned above the iirst solenoid and having one lead connected to the anode whereby when the negative side of a direct current circuit is con- 6 nected to the cathode and the positive side is connected to the leads of both solenoids, the rod will rise to a rst position starting an arc between the cathode and the anode and will then rise to a second position whereby the closure member will snuff out the arc.

WARREN G. TAYLOR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,300,251 Davis Apr. 15, 1919 1,816,168 Berthold July 28, 1931 1,941,567 Marti Jan. 2, 1934 2,053,930 Winter Sept. 8, 1936 2,072,993 Ulrey Mar. 9, 1937 2,169,818 Scott Aug. 15, 1939 2,203,579 Randolph June 4, 1940 2,221,569 Berkey Nov. 12, 1940 2,248,574 Knight July 8, 1941 2,292,137 Livingston Aug. 4, 1942 2,294,388 Dawson Sept. 1, 1942 2,341,562 Klemperer Feb. 15, 1944 2,388,430 Mikhalapov Nov. 6, 1945 

